1. Field of the Invention
The present invention relates to a carrier tape used for packing surface-mounting type electronic devices and a method for fabricating such a carrier tape. The present invention also relates to a taped package having electronic devices packed by such a carrier tape.
2. Description of the Related Art
Conventionally, electronic devices, and in particular surface-mounting type electronic devices, are sometimes packed using trays or embossed type carrier tapes, and the thus formed packages are shipped to users. The users use the electronic devices in such packages in automated mounting machines to mount the electronic devices to the surface of the printed wiring boards or the like.
FIG. 14 of the attached drawings is a perspective view of the tray. The tray has a plurality of square cavities (pockets) 41 arranged in a matrix pattern, so that the electronic devices can be accommodated in the pockets 41.
FIG. 15 of the attached drawings is a perspective view of the embossed type carrier tape. In this figure, the numeral 50 shows the embossed type carrier tape, the numeral 60 shows a top cover tape, and the numeral 70 shows a reel. The embossed type carrier tape 50 has a row of pockets 51 and connecting wall portions 52 interconnecting adjacent pockets 51. The embossed type carrier tape 50 is made from a plastic sheet (tape) which is embossed by vacuum forming or heat pressing, to form the pockets 51. The carrier tape 50 also has feed holes 53.
The package of electronic devices is used as follows; the electronic devices are put in the pockets 51 of the carrier tape 50, the pockets 51 are covered by the top cover sheet 60 bonded to the carrier tape 50, and the carrier tape 50 is wound on the reel 70. The manufacturer then ships the reel 70 as a package, and the user thus uses the reel 70 in an automated mounting machine to mount the electronic devices to the surface of a printed wiring board or the like. After the mounting operation, the carrier tape 50 is severed into small pieces by a cutter attached to the automated mounting machine, and the severed carrier tape 50 is disposed of.
In the mounting operation of the electronic devices to the surface of the printed wiring board by the automated mounting machine, it is generally recognized that the electronic devices packed in the carrier tape can be mounted to the printed wiring board at a considerably faster speed than that of the electronic devices packed in the tray. However, since the embossed type carrier tape 50 is made from a plastic sheet having a uniform thickness and the pockets 51 are embossed by vacuum forming or heat pressing, there are problems that if a relatively thick plastic sheet is used, it is not easy to wind the embossed type carrier tape 50 on the reel 70, and if the relatively thin plastic sheet is used, the strength of the pockets 51 is insufficient to reliably accommodate, in particular, large articles, so that the bottoms of the pockets may collapse while the embossed type carrier tape is wound on the reel, to cause the articles in the pockets to be damaged (for example, the external leads may be deformed in the case of a QFP (Quad Flat Package) type LSI). In addition, it is difficult to accurately form the pockets which are designed to accommodate larger articles. Therefore, conventionally, there is a problem that larger articles must be packed in the trays. FIG. 13 in the attached drawings is a side view of the package, illustrating the problem of the prior art. This figure shows that the embossed type carrier tape is wound on the reel and the bottoms of the pockets located on the outer side of the bent portion of the tape are collapsed.